Method for manufacturing an organic semiconductor device, as well as organic semiconductor device, electronic device, and electronic apparatus

ABSTRACT

An organic semiconductor device having a gate electrode, a source electrode, a drain electrode, an organic semiconductor layer, a gate insulation layer, and a substrate. The substrate of the semiconductor device having an underlayer including an organic polymer material having a liquid crystal core. The underlayer is oriented in a specific direction formed between the substrate and the organic semiconductor layer so as to orient the organic semiconductor layer along the orientation of the underlayer.

BACKGROUND

This is a Division of application Ser. No. 11/372,213 filed Mar. 10,2006. The disclosure of the prior application is hereby incorporated byreference herein in its entirety.

1. Technical Field

The present invention relates to a method for manufacturing an organicsemiconductor device, as well as an organic semiconductor device, anelectronic device, and an electronic apparatus.

2. Related Art

In recent years, the development of a thin-film transistor using anorganic material (organic semiconductor material) that showssemiconductive electric conduction has been being progressed. Such athin-film transistor can be formed by the solution process of asemiconductor layer that does not require an environment of hightemperature and high vacuum. Also, due to some advantages including thesuitability for a thinner and lighter device, flexibility, and lowmaterial cost, etc., such a transistor is expected to be promising as aswitching element of a flexible display, etc.

As such a thin-film transistor, a transistor wherein a gate electrode, asource electrode, a drain electrode, an organic semiconductor layer, anda gate insulation layer are configured of organic materials has beenproposed. “Inkjet printing of polymer thin film transistors”, TakeoKawase et al., in Thin Solid Films 2003 (pp. 279 to 287) is an exampleof related art.

By the way, as a property parameter for evaluating the performance of athin-film transistor, the carrier mobility in a semiconductor layer canbe named. The larger the carrier mobility in a semiconductor layerbecomes, the faster the operating speed of a thin-film transistorbecomes.

However, the carrier mobility of an organic semiconductor layer is lowerby two or more digits than that of an inorganic semiconductor layer,which is generally configured of silicon, etc. Therefore, it is verydifficult to increase the operating speed of a thin-film transistorhaving an organic semiconductor layer.

Hence, various studies have been in progress for further improvement ofcarrier mobility, in view of practical use.

SUMMARY

An advantage of the invention is to provide a method for manufacturingan organic semiconductor device that can achieve an easy manufacturingof an organic semiconductor device of high operating speed, as well asan organic semiconductor device of high operating speed, and anelectronic device and an electronic apparatus that are highly reliable.

The above advantage is achieved by the invention described below.

According to a first aspect of the invention, a method for manufacturingan organic semiconductor device having a gate electrode, a sourceelectrode, a drain electrode, an organic semiconductor layer, a gateinsulation layer, and a substrate includes: forming, on the substrate,an underlayer that contains an organic polymer material having a liquidcrystal core and is oriented in a specific direction, before forming theorganic semiconductor layer; and forming the organic semiconductor layerso as to orient the organic semiconductor layer along the orientation ofthe underlayer. In this method, the gate insulation layer insulates thesource electrode and the drain electrode from the gate electrode; andthe substrate supports the gate electrode, the source electrode, thedrain electrode, the organic semiconductor layer, and the gateinsulation layer.

By the above method, an organic semiconductor device of high operatingspeed can be manufactured easily.

It is preferable that the method for manufacturing an organicsemiconductor device according to the first aspect of the inventionfurther includes: forming the source electrode and the drain electrodeon the underlayer before forming the organic semiconductor layer; andforming the organic semiconductor layer with part of the organicsemiconductor layer contacting the underlayer so as to orient theorganic semiconductor layer along the orientation of the underlayer.

By the above method, an organic semiconductor device having a top-gateorganic thin-film transistor of high operating speed can be manufacturedeasily.

It is preferable that the method for manufacturing an organicsemiconductor device according to the first aspect of the inventionfurther includes: forming the gate electrode on the underlayer beforeforming the organic semiconductor layer; forming the gate insulationlayer with part of the gate insulation layer contacting the underlayerso as to orient the gate insulation layer along the orientation of theunderlayer; and forming the organic semiconductor layer so as to orientthe organic semiconductor layer along the orientation of the gateinsulation layer.

By the above method, an organic semiconductor device having abottom-gate organic thin-film transistor of high operating speed can bemanufactured easily.

It is preferable that the method for manufacturing an organicsemiconductor device according to the first aspect of the inventionfurther includes: forming the source electrode and the drain electrodeon the gate insulation layer before forming the organic semiconductorlayer; and forming the organic semiconductor layer with part of theorganic semiconductor layer contacting the gate insulation layer so asto orient the organic semiconductor layer along the orientation of thegate insulation layer.

By the above method, an organic semiconductor device having abottom-gate organic thin-film transistor of high operating speed can bemanufactured easily.

In the method for manufacturing an organic semiconductor deviceaccording to the first aspect of the invention, it is preferable that amaterial configuring the underlayer and a material configuring the gateinsulation layer are the same.

By the above method, the orientivity of the gate insulation layer alongthe orientation of the underlayer is more ensured.

In the method for manufacturing an organic semiconductor deviceaccording to the first aspect of the invention, it is preferable thatthe source electrode and the drain electrode are formed along a specificdirection with an interval in between.

By the above method, the carrier mobility in the channel region of theorganic semiconductor layer can be improved.

In the method for manufacturing an organic semiconductor deviceaccording to the first aspect of the invention, it is preferable thatthe underlayer is formed after performing the orientation processing ofthe substrate.

By the above method, the orientivity of the underlayer is more ensured.

In the method for manufacturing an organic semiconductor deviceaccording to the first aspect of the invention, it is preferable thatthe orientation processing is performed by means of rubbing.

By the rubbing method, the orientation of the substrate becomesrelatively easy.

In the method for manufacturing an organic semiconductor deviceaccording to the first aspect of the invention, it is preferable thatthe underlayer is formed by polymerizing a compound containing at leasta single or two or more organic low-molecular materials having apolymeric group and a liquid crystal core.

By the above method, a more highly oriented underlayer can be formed.

In the method for manufacturing an organic semiconductor deviceaccording to the first aspect of the invention, it is preferable thatthe compound shows a liquid crystal phase under room temperature.

By the above method, a more highly oriented underlayer can be formed.

In the method for manufacturing an organic semiconductor deviceaccording to the first aspect of the invention, it is preferable thatthe compound has a nematic phase.

By the above method, a more highly oriented underlayer can be formed.

In the method for manufacturing an organic semiconductor deviceaccording to the first aspect of the invention, it is preferable thatthe compound has a smectic phase.

By the above method, a more highly oriented underlayer can be formed.

According to a second aspect of the invention, an organic semiconductordevice includes: a gate electrode; a source electrode; a drainelectrode; an organic semiconductor layer; a gate insulation layer thatinsulates the source electrode and the drain electrode from the gateelectrode; and a substrate that supports the gate electrode, the sourceelectrode, the drain electrode, the organic semiconductor layer, and thegate insulation layer. In this organic semiconductor device, anunderlayer that contains an organic polymer material having a liquidcrystal core and is oriented in a specific direction is formed betweenthe substrate and the organic semiconductor layer so as to orient theorganic semiconductor layer along the orientation of the underlayer.

With the above device, an organic semiconductor device of high operatingspeed can be obtained.

In the organic semiconductor device according to the second aspect ofthe invention, it is preferable that the orientation of the underlayeris approximately in parallel to the direction from either of the sourceelectrode or the drain electrode to the other.

With the above device, the carrier mobility in the channel region of theorganic semiconductor layer can be improved.

In the organic semiconductor device according to the second aspect ofthe invention, it is preferable that the organic semiconductor layercontains a polymer organic semiconductor material.

With the above device, orientation can be performed relatively easily bya simple method due to the superiority in carrier transportation of apolymer organic semiconductor material.

In the organic semiconductor device according to the second aspect ofthe invention, it is preferable that the organic semiconductor layer isconfigured of an organic semiconductor material containing mainly anaryl group.

Many organic polymer materials used as a material configuring theunderlayer have an aryl group. Therefore, by configuring an organicsemiconductor layer using an organic semiconductor material having anaryl group as a main material, high adhesiveness with the underlayer canbe obtained.

According to a third aspect of the invention, an electronic deviceincludes the organic semiconductor device according to the second aspectof the invention.

With the above device, a highly reliable electronic device can beobtained.

According to a fourth aspect of the invention, an electronic apparatusincludes the electronic device according to the third aspect of theinvention.

With the above apparatus, a highly reliable electronic apparatus can beobtained.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanyingdrawings, wherein like numbers reference like elements.

FIG. 1 is a block diagram showing the configuration of an active-matrixdevice to which an organic semiconductor device according to the secondaspect of the invention is applied.

FIGS. 2A and 2B are diagrams (a vertical cross section and a plan view)showing the configuration of an organic thin-film transistor included inan active-matrix device according to a first embodiment.

FIGS. 3A, 3B, 3C, 3D, and 3E are diagrams (vertical cross sections) fordescribing a method for manufacturing the organic thin-film transistorshown in FIGS. 2A and 2B.

FIGS. 4F and 4G are diagrams (vertical cross sections) for describing amethod for manufacturing the organic thin-film transistor shown in FIGS.2A and 2B.

FIG. 5 is a diagram (vertical cross section) showing the configurationof an organic thin-film transistor included in an active-matrix deviceaccording to a second embodiment.

FIG. 6 is a vertical cross section showing a third embodiment wherein anelectrophoretic display device is taken as an example.

FIG. 7 is a perspective view showing a fourth embodiment wherein anelectronic apparatus according to the fourth aspect of the invention isapplied to an electronic paper.

FIGS. 8A and 8B are diagrams showing a fifth embodiment wherein anelectronic apparatus according to the fourth aspect of the invention isapplied to a display.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Embodiments of a method for manufacturing an organic semiconductordevice, as well as an organic semiconductor device, an electronicdevice, and an electronic apparatus according to the invention will nowbe described in detail.

The following are examples where the organic semiconductor deviceaccording to the invention is applied to an active-matrix device.

First Embodiment

A first embodiment of an active-matrix device will be described.

FIG. 1 is a block diagram showing the configuration of an active-matrixdevice to which an organic semiconductor device according to the secondaspect of the invention is applied. FIGS. 2A and 2B are diagrams (avertical cross section and a plan view) showing the configuration of anorganic thin-film transistor included in an active-matrix deviceaccording to a first embodiment. FIGS. 3A to 3E and FIGS. 4F and 4G arediagrams (vertical cross sections) for describing a method formanufacturing the organic thin-film transistor shown in FIGS. 2A and 2B.In addition, in the following description, the upper side of FIGS. 2 to4 is expressed as “top” and the lower side is expressed as “bottom.”

An active-matrix device 300 shown in FIG. 1 has: a substrate 500; aplurality of data lines 301 and a plurality of scanning lines 302, bothof which are provided on the substrate 500 and orthogonal to each other;an organic thin-film transistor 1 (hereinafter referred to as “thin-filmtransistor 1”) provided near each intersection of the data line 301 andthe scanning line 302; and pixel electrodes 303.

Further, a gate electrode 50 included in the thin-film transistor 1 iscoupled to the scanning line 302, a source electrode 20 a also includedin the thin-film transistor 1 is coupled to the data line 301, and adrain electrode 20 b also included in the thin-film transistor 1 iscoupled to the pixel electrode (individual electrode) 303, which will bedescribed later.

As shown in FIG. 2A, the thin-film transistor 1 according to the firstembodiment is a top-gate thin-film transistor and has: a buffer layer(underlayer) 60 provided on the substrate 500; the source electrode 20 aand the drain electrode 20 b both provided on the buffer layer 60 withan interval in between; an organic semiconductor layer 30 provided incontact with the source electrode 20 a and the drain electrode 20 b; agate insulation layer 40 placed between the organic semiconductor layer30 and the gate electrode 50; and a protective layer 70 provided so asto cover the foregoing layers.

The configuration of each part will be described sequentially.

The substrate 500 supports each of the layers (parts) configuring thethin-film transistor 1 (active-matrix device 300).

As the substrate 500, such materials as: glass substrates; plasticsubstrates (resin substrates) configured of polyethylene terephthalate(PET), polyethylene naphthalate (PEN), polyethersulfone (PES), aromaticpolyester (liquid crystal polymer), polyimide (PI), etc.; quartzsubstrates; silicon substrates; metal substrates; gallium arsenidesubstrates; etc. can be used.

In order to give flexibility to the thin-film transistor 1, a plasticsubstrate or a thin (relatively thin) metal substrate is selected as thesubstrate 500.

On the substrate 500, the buffer layer 60 is provided.

The buffer layer 60 is oriented in a specific direction, which is, inthe first embodiment, approximately in parallel to the channel-lengthdirection (horizontal direction in FIG. 2A) of the channel region. Thebuffer layer 60 oriented as such has a function for orienting theorganic semiconductor layer 30, which will be described later.

With the above function, the orientation of the organic semiconductorlayer 30 can be determined in a specific direction without complicatingthe configuration of the thin-film transistor 1 and, at the same time,the carrier mobility in the channel region can be improved. As a result,the thin-film transistor 1 of high operating speed and further theactive-matrix device 300 of high operating speed can be obtained.

The buffer layer 60 is mainly configured of an organic polymer materialhaving a liquid crystal core. Such a configuration contributes to theextremely high orientivity of the buffer layer 60. Therefore, theorientivity of the organic semiconductor layer 30 that is oriented inaccordance with the buffer layer 60 also becomes very high, whichimproves the carrier mobility in the channel region of the thin-filmtransistor 1.

In the above description, the oriented buffer layer 60 means that mostof the components in the organic polymer material that configures thebuffer layer 60 are lined in approximately the same direction. However,it is allowable if some of the components are placed in quite differentdirections.

Examples of the liquid crystal core (a mesogen group) contained in suchan organic polymer material include one of or a combination of two ormore of the following: a benzene ring, a naphthalene ring, an anthracenering, and a cyclohexane ring. Such organic polymer materials having aliquid crystal core have a high orientivity and therefore are preferableas a material configuring the buffer layer 60. Especially, a compoundthat is configured of at least two or more kinds of organiclow-molecular materials having a polymeric group, as a polymerizedprecursor, as well as a liquid crystal core and shows a liquid crystalphase under room temperature is more preferable as a material of thebuffer layer 60. It is much more preferable if the compound shows anematic phase or a smectic phase under room temperature.

Further, by configuring the buffer layer 60 using such organic polymermaterials, which have a low hygroscopicity, the infiltration of moistureinto the organic semiconductor layer 30 can also be prevented.

Furthermore, by using a compound having an arylamine skeleton as amaterial configuring the organic semiconductor layer 30, as describedlater, the adhesiveness between the organic semiconductor layer 30 andthe buffer layer 60 can be improved.

In addition, the above organic polymer material, which is highlyinsulative, is also preferable as a material configuring the gateinsulation layer 40 in a second embodiment, which will be describedlater.

The average thickness of the buffer layer 60 is not limited to butpreferred to be approximately 1 to 1000 nm or, more preferably, 10 to700 nm.

On the buffer layer 60, the source electrode 20 a and the drainelectrode 20 b are provided along the orientation of the buffer layer 60with an interval in between.

Examples of the material configuring the source electrode 20 a and thedrain electrode 20 b include: Au, Ag, Cu, Pt, Ni, Cr, Ti, Ta, and Al; ormetal materials such as alloys containing the foregoing materials. Theforegoing materials can be used singly or as a combination of two ormore.

Among the above materials, ones that mainly contain Au, Ag, Cu, and Pt;or alloys containing the foregoing are preferable as the materialconfiguring the source electrode 20 a and the drain electrode 20 b.Since such materials have a relatively large work function, the use ofsuch materials in configuring the source electrode 20 a, in the casewhere the organic semiconductor layer 30 is p-type, improves theinjection efficiency of an electron hole (carrier) into the organicsemiconductor layer 30.

In addition, the average thickness of the source electrode 20 a and thedrain electrode 20 b is not limited to but preferred to be approximately10 to 2000 nm or, more preferably, 50 to 1000 nm.

The interval between the source electrode 20 a and the drain electrode20 b, or a channel length L shown in FIG. 2B, is preferred to beapproximately 2 to 30 μm or, more preferably, 2 to 20 μm. By setting thechannel length L within the foregoing range, the properties of thethin-film transistor 1 can be improved. Especially, the on-current canbe increased.

Further, the width of the source electrode 20 a and the drain electrode20 b, or a channel width W shown in FIG. 2B, is preferred to beapproximately 0.1 to 5 mm or, more preferably, 0.3 to 3 mm. By settingthe channel width W within the foregoing range, the parasiticcapacitance can be reduced, which prevents the degradation in propertiesof the thin-film transistor 1. Furthermore, the larger sizing of thethin-film transistor 1 can also be prevented.

The organic semiconductor layer 30 is provided in contact with thesource electrode 20 a and the drain electrode 20 b.

The organic semiconductor layer 30 contacts the buffer layer 60 by onepart (the channel region). Due to the contact, the organic semiconductorlayer 30 is oriented along the orientation of the buffer layer 60, orthe channel length, which is the direction from either of the sourceelectrode 20 a or the drain electrode 20 b to the other.

Examples of the material configuring the organic semiconductor layer 30include: polymer organic semiconductor materials such aspoly(3-alkylthiophene), poly(3-hexylthiophene) (P3HT),poly(3-octylthiophene), poly(2,5-thienylenevinylene) (PTV),poly(para-phenylenevinylene) (PPV), poly(9,9-dioctylfluorene) (PFO),poly(9,9-dioctylfluorene-cobis-N,N′-(4-methoxyphenyl)-bis-N,N′-phenyl-1,4-phenylenediamine)(PFMO), poly(9,9-dioctylfluorene-co-benzothiaziazole) (BT),fluorene-triarylamine copolymer, triarylamine series polymer, andfluorene-bithiophene copolymer (F8T2); as well as low-molecular organicsemiconductor materials such as fullerene, metal phthalocyanine or thederivatives of the same, acene molecular materials such as anthracene,tetracene, pentacene, hexacene, etc., and α-oligothiophenes such asquaterthiophene (4T), sexithiophene (6T), octithiophene (8T),dihexylquaterthiophene (DH4T), dihexylsexithiophene (DH6T), etc. Theabove materials can be used singly or as a combination of two or more.

Among the above materials, ones that mainly contain a polymer organicsemiconductor material are especially preferable. This is becausepolymer organic semiconductor materials are superior in carriertransportation and can be oriented relatively easily by a simple method.

Further, since the organic semiconductor layer 30 that is mainlyconfigured of a polymer organic semiconductor material can be madethinner and lighter and is also superior in flexibility, it is suitableto be applied to the thin-film transistor 1 that is used as a switchingelement of a flexible display, etc.

Many of the organic polymer materials used for configuring the bufferlayer 60 have an aryl group. Therefore, by configuring the organicsemiconductor layer 30 using an organic semiconductor material having anaryl group, such as fluorene-triarylamine copolymers; triarylamineseries polymers; and acene molecular materials, as a main material, highadhesiveness with the buffer layer 60 can be obtained.

The average thickness of the organic semiconductor layer 30 is notlimited to but preferred to be approximately 0.1 to 1000 nm, morepreferably, 1 to 500 nm or, much more preferably, 1 to 100 nm.

In addition, the organic semiconductor layer 30 can be a configurationthat is selectively provided in the region (channel region) between thesource electrode 20 a and the drain electrode 20 b or anotherconfiguration that is provided to cover almost all over the sourceelectrode 20 a and the drain electrode 20 b.

The gate insulation layer 40 is provided so as to cover the organicsemiconductor layer 30, the source electrode 20 a, and the drainelectrode 20 b.

The gate insulation layer 40 insulates the gate electrode 50, which willbe described later, from the source electrode 20 a and the drainelectrode 20 b.

It is preferable that the gate insulation layer 40 is mainly configuredof an organic material (organic polymer material, especially). The gateinsulation layer 40 containing an organic polymer material as a mainmaterial is easy to be formed and, at the same time, can improve theadhesiveness with the organic semiconductor layer 30.

Examples of such an organic polymer material include: acrylic resinssuch as polystyrene, polyimide, polyamidimide, polyvinylphenylene,polycarbonate (PC), and polymethylmethacrylate (PMMA); fluoric resinssuch as polytetrafluoroethylene (PTFE); phenolic resins such aspolyvinylphenol or novolac resin; olefinic resins such as polyethylene,polypropylene, polyisobutylene, polybutene; etc. The foregoing materialscan be used singly or as a combination of two or more.

The average thickness of the gate insulation layer 40 is not limited tobut preferred to be approximately 10 to 5000 nm or, more preferably, 100to 2000 nm. By setting the thickness of the gate insulation layer 40within the foregoing range, the operating voltage of the thin-filmtransistor 1 can be lowered while ensuring the insulation of the gateelectrode 50 from the source electrode 20 a and the drain electrode 20b.

In addition, as a material configuring the gate insulation layer 40,inorganic materials such as SiO₂ (silicon oxide), Si₂N₃ (siliconnitride), Al₂O₃, Ta₂O₅, BST, PZT, etc. can also be used.

Further, the gate insulation layer 40 is not limited to a single-layerconfiguration but can be a laminated configuration including a pluralityof above-described organic or inorganic materials.

At a specific position on the gate insulation layer 40, that is, aposition corresponding to the region between the source electrode 20 aand the drain electrode 20 b, the gate electrode 50 for applying anelectric field to the organic semiconductor layer 30 is provided.

The material configuring the gate electrode 50 only needs to be, withoutlimitation, a publicly known electrode material. Specifically, thefollowing can be named: metal materials such as Pd, Pt, Au, W, Ta, Mo,Al, Cr, Ti, and Cu or alloys including the foregoing; carbon materialssuch as carbon black, carbon nanotube, fullerene, etc.; polythiophenessuch as polyacethylene, polypyrrole, and poly-ethylenedioxythiophene(PEDOT); conductive polymer materials such as polyaniline,poly(p-phenylene), poly(p-phenylenevinylene), polyfluorene,polycarbazole, and polysilane or the derivatives of the foregoing; etc.

The average thickness of the gate electrode 50 is not limited to butpreferred to be approximately 0.1 to 2000 nm or, more preferably, 1 to1000 nm.

Further, the protective layer 70 is provided so as to cover theabove-described layers.

The protective layer 70 has functions for preventing the infiltration ofmoisture into the organic semiconductor layer 30 and preventing theshort circuit between adjoining thin-film transistors 1 that is causedat the contact of a foreign material to the gate electrode 50.

Examples of the material configuring the protective layer 70 are thesame as those for the gate insulation layer 40.

The average thickness of the protective layer 70 is not limited to butpreferred to be approximately 0.01 to 10 μm or, more preferably, 0.1 to5 μm.

In addition, the protective layer 70 is provided according to need andcan be omitted.

In the above thin-film transistor 1, when a gate voltage is applied tothe gate electrode 50 with a voltage applied between the sourceelectrode 20 a and the drain electrode 20 b, a channel is formed on theorganic semiconductor layer 30, near the interface with the gateinsulation layer 40. With the move of a carrier (electron hole) withinthe channel region, a current runs between the source electrode 20 a andthe drain electrode 20 b.

That is, in the off-state where no voltage is applied to the gateelectrode 50, even when a voltage is applied between the sourceelectrode 20 a and the drain electrode 20 b, there runs only a slightcurrent because there are almost no carriers in the organicsemiconductor layer 30.

On the other hand, in the on-state where a voltage is applied to thegate electrode 50, a charge is induced in a region on the organicsemiconductor layer 30 facing the gate insulation layer 40, and then achannel (carrier path) is formed. When a voltage is applied between thesource electrode 20 a and the drain electrode 20 b under the abovestate, a current runs through the channel region.

The above active-matrix device 300 can be manufactured as follows.

A method for manufacturing the active-matrix device 300 (a method formanufacturing an organic semiconductor device according to the firstembodiment of the invention) will be described below.

In addition, the following mainly describes a method for manufacturingthe thin-film transistor 1.

A1: Pretreatment (Refer to FIG. 3 a)

First, the substrate 500 is prepared and an orientation processing isperformed on the top surface of the substrate 500.

With the above processing, the orientation of the buffer layer 60 ismore ensured.

Examples of the orientation method include rubbing, laser processing,blast processing, etc. Among the foregoing, rubbing is especiallypreferable.

The rubbing in the above description is a processing method wherein thetop surface of the substrate 500 is rubbed in a specific direction bypressing a roller 910, which is wrapped with a cloth 900 made ofpolyamide (nylon) for example, against the substrate 500 at a specificpressure. By such a rubbing method, the orientation processing of thesubstrate 500 can be performed relatively easily.

Conditions for performing the rubbing, which vary a little withmaterials of the substrate 500, etc., are not limited to but include thefollowing, for example. The press depth is preferred to be approximately0.01 to 1 mm or, more preferably, 0.1 to 0.5 mm. The rotationalfrequency is preferred to be approximately 10 to 5000 rpm or, morepreferably, 100 to 1000 rpm. Further, the rolling rate is preferred tobe approximately 0.01 to 50 m/min or, more preferably, 0.1 to 10 m/min.

A2: Forming a Buffer Layer (Refer to FIG. 3 b)

Next, the buffer layer 60 is formed on the oriented surface of thesubstrate 500.

The buffer layer 60 can be formed by directly using the above-describedorganic polymer materials. However, it is preferable to form the bufferlayer 60 by using the precursors of the organic polymer materials. Bythe latter method, the buffer layer 60 having a higher orientivity canbe formed.

Specifically, the buffer layer 60 can be formed by: preparing a solutionthat is a compound including a single or two or more organiclow-molecular materials having a polymeric group and a liquid crystalcore; supplying the solution onto the substrate 500 to form a liquidfilm; removing the solvent (deliquoring) from the liquid film; andpolymerizing the organic low molecules. Further, the buffer layer 60 canbe a solution that is a compound including a single or two or moreorganic low-molecular materials having a polymeric group and a liquidcrystal core and can be formed by supplying the solution onto thesubstrate 500 to form a liquid film and polymerizing the organic lowmolecules.

Examples of the polymeric group contained in the organic low moleculesinclude: a (meta) acryl group, an epoxy group, a vinyl group, a styrenegroup, an oxetane group, etc.

As examples of such organic low-molecular materials, there are chemicalcompounds expressed in chemical formulas 1 to 19 below.

Further, examples of the method for supplying a solution onto thesubstrate 500 include: spin coating, casting, microgravure coating,gravure coating, bar coating, roll coating, wire-bar coating, dipcoating, spray coating, screen printing, flexographic printing, offsetprinting, inkjetting, microcontact printing, etc. The foregoing methodscan be employed singly or as a combination of two or more.

Furthermore, examples of the method for polymerizing an organiclow-molecular material include photopolymerization reaction, thermalpolymerization reaction, etc. In addition, the type of reaction can beset in accordance with: the type of organic low-molecular material, thetype of polymerization initiator to be added in a solution, the type ofpolymerization promoter, etc.

A3: Forming a Source Electrode and a Drain Electrode (Refer to FIG. 3C)

Next, the source electrode 20 a and the drain electrode 20 b are formedon the buffer layer 60 along the orientation of the buffer layer 60 witha specific interval in between.

First, a metal film (metal layer) is formed on the buffer layer 60. Themetal film can be formed by means of, for example: chemical vapordeposition (CVD) methods such as plasma CVD, thermal CVD, laser CVD,etc.; dry plating methods such as vacuum deposition, sputtering(low-temperature sputtering), ion plating, etc.; wet plating methodssuch as electrolytic plating, immersion plating, electroless plating,etc.; thermal spraying; sol-gel methods; MOD methods; metallic-foilbonding; etc.

After applying a photoresist material on the metal film and hardeningthe photoresist material, a photoresist layer that is shapedcorrespondingly to the source electrode 20 a and the drain electrode 20b is formed. Using the photoresist layer as a mask, the unnecessary partof the metal film is removed. Examples of the method for removing themetal film include one of or a combination of two or more of thefollowing: physical etching methods such as plasma etching, reactive ionetching, beam etching, light-assisted etching, etc.; and chemicaletching methods such as wet etching, etc.

After that, by removing the photoresist layer, the source electrode 20 aand the drain electrode 20 b can be obtained.

Further, the source electrode 20 a and the drain electrode 20 b can alsobe formed by, for example: supplying a conductive material containingconductive particles onto the buffer layer 60 to form a liquid film; andperforming a posttreatment (heating, infrared radiation,ultrasonication, etc. for example) to the liquid film according to need.

In addition, as the method for supplying a conductive material, the onesdescribed in the above step A2 can be employed.

Further, in the step A3, the data lines 301 and the pixel electrodes 303are also formed.

A4: Forming an Organic Semiconductor Layer (Refer to FIG. 3D)

Next, the organic semiconductor layer 30 is formed so that the organicsemiconductor layer 30 contacts the source electrode 20 a and the drainelectrode 20 b.

In the step A4, the organic semiconductor layer 30 is oriented along theorientation of the buffer layer 60, with part of the organicsemiconductor layer 30 contacting part of the buffer layer 60 that isexposed in the region between the source electrode 20 a and the drainelectrode 20 b.

Therefore, in the region (channel region) between the source electrode20 a and the drain electrode 20 b, the organic semiconductor layer 30 isoriented along the channel-length direction.

The organic semiconductor layer 30 can also be formed by, for example:supplying a solution containing an organic semiconductor material or theprecursor of an organic semiconductor material onto a specific region onthe buffer layer 60, including the region between the source electrode20 a and the drain electrode 20 b, to form a liquid film; and performinga posttreatment (heating, infrared radiation, ultrasonication, etc. forexample) to the liquid film according to need.

In addition, as the method for supplying a solution, the ones describedin the step A2 can be employed.

A5: Forming a Gate Insulation Layer (Refer to FIG. 3 e)

Next, the gate insulation layer 40 is formed so as to cover the sourceelectrode 20 a, the drain electrode 20 b, and the organic semiconductorlayer 30.

The gate insulation layer 40 can be formed by the same method as for theorganic semiconductor layer 30.

A6: Forming a Gate Electrode (Refer to FIG. 4 f)

Next, the gate electrode 50 is formed on the gate insulation layer 40,at a position corresponding to the region between the source electrode20 a and the drain electrode 20 b.

The gate electrode 50 can be formed by the same method as for the sourceelectrode 20 a and the drain electrode 20 b.

Further, in the step A6, the scanning lines 302 are also formed.

In addition, in the first embodiment, the scanning lines 302, which areformed separately from the gate electrode 50, can also be formed bysuccessively forming the gate electrodes 50 of adjoining thin-filmtransistors 1.

A7: Forming a Protective Layer (Refer to FIG. 4 g)

Next, the protective layer 70 is formed on the gate insulation layer 40.

The protective layer 70 can be formed by the same method as for theorganic semiconductor layer 30.

Second Embodiment

Next, a second embodiment of an active-matrix device will be described.

FIG. 5 is a diagram (vertical cross section) showing the configurationof an organic thin-film transistor included in an active-matrix deviceaccording to the second embodiment. In addition, in the followingdescription, the upper side of FIG. 5 is expressed as “top” and thelower side is expressed as “bottom.”

The following description for the second embodiment is mainly for thedifferences from the first embodiment and the descriptions of the samematters as for the first embodiment are omitted.

In the second embodiment, the thin-film transistor 1 has a bottom-gateconfiguration. The other matters are the same as in the firstembodiment.

As shown in FIG. 5, the thin-film transistor 1 in the second embodimenthas: the buffer layer (underlayer) 60 provided on the substrate 500; thegate electrode 50 provided on the buffer layer 60; the gate insulationlayer 40 provided on the buffer layer 60 so as to cover the gateelectrode 50; the source electrode 20 a and the drain electrode 20 bprovided on the gate insulation layer 40 with an interval in between;the organic semiconductor layer 30 provided in contact with the sourceelectrode 20 a and the drain electrode 20 b; and the protective layer 70so as to cover the foregoing layers.

In the thin-film transistor 1, the gate insulation layer 40 is orientedalong the orientation of the buffer layer 60, and the organicsemiconductor layer 30 is oriented along the orientation of the gateinsulation layer 40.

Under such circumstances, it is preferable that the material configuringthe gate insulation layer 40 and the material configuring the bufferlayer 60 are the same, although the case where the two materials aredifferent is also allowable. By such a method, the orientation of thegate insulation layer along the orientation of the buffer layer 60 ismore ensured. Therefore, even with a distance between the organicsemiconductor layer 30 and the buffer layer 60, the organicsemiconductor layer 30 can surely be oriented along the orientation ofthe buffer layer 60.

In addition, as described above, the organic polymer material used forthe buffer layer 60, which is highly insulative, is also preferable as amaterial for configuring the gate insulation layer 40.

With the configuration according to the second embodiment, the sameeffect as in the first embodiment can be obtained.

The above thin-film transistor 1 can be manufactured as follows.

B1: Pretreatment

The same processing as in the step A1 is performed.

B2: Forming a Buffer Layer

The same processing as in the step A2 is performed.

B3: Forming a Gate Electrode

The same processing as in the step A6 is performed.

B4: Forming a Gate Insulation Layer

The same processing as in the step A5 is performed.

In the step B4, the gate insulation layer 40 is oriented along theorientation of the buffer layer 60, with part of the gate insulationlayer 40 contacting the buffer layer 60 that is exposed from the gateelectrode 50.

B5: Forming a Source Electrode and a Drain Electrode

The same processing as in the step A3 is performed.

B6: Forming an Organic Semiconductor Layer

The same processing as in the step A4 is performed.

In the step B6, the organic semiconductor layer 30 is oriented along theorientation of the gate insulation layer 40, with part of the organicsemiconductor layer 30 contacting the gate insulation layer 40 that isexposed in the region between the source electrode 20 a and the drainelectrode 20 b. That is, the organic semiconductor layer 30 is orientedalong the orientation of the buffer layer 60.

B7: Forming a Protective Layer

The same processing as in the step A7 is performed.

Electronic Device

Next, as an example of an electronic device according to a thirdembodiment of the invention, an electrophoretic display device in whichthe above-described active-matrix device is provided will be described.

FIG. 6 is a vertical cross section showing the third embodiment whereinan electrophoretic display device is taken as an example. In addition,in the following description, the upper side of FIG. 6 is expressed as“top” and the lower side is expressed as “bottom.”

An electrophoretic display device 200 shown in FIG. 6 is configured ofthe above active-matrix device 300 and an electrophoretic display unit400 provided on the active-matrix device 300.

The electrophoretic display unit 400 is configured of: a transparentsubstrate 404 having a transparent electrode (common electrode) 403; andmicrocapsules 402 fixed on the transparent electrode 403 with a binder405.

Further, the active-matrix device 300 and the electrophoretic displayunit 400 are bonded so that the microcapsules 402 contact the pixelelectrodes 303.

In each of the microcapsules 402, an electrophoretic dispersion liquid420 containing a plurality of different electrophoretic particles isencapsulated. In the third embodiment, the electrophoretic particles aretwo kinds of electrophoretic particles 421 and 422 having differentcharges and colors (hues).

In the above electrophoretic display device 200, when a selection signal(selection voltage) is supplied to a single or a plurality of thescanning lines 302, the thin-film transistors 1 coupled to the scanninglines to which the selection signal (selection voltage) is supplied areturned on.

By the above method, the data lines 301 and the pixel electrodes 303that are coupled to the relevant thin-film transistors 1 becomevirtually conductive to each other. Under such circumstances, if adesired data (voltage) is supplied to the data lines 301, the data(voltage) is supplied to the pixel electrodes 303.

By the above method, an electric field is generated between each pixelelectrode 303 and the transparent electrode 403, and the electrophoreticparticles 421 and 422 electrophoretically migrate toward either of theelectrodes in accordance with: the direction and strength of theelectric field, the properties of the electrophoretic particles 421 and422, etc.

On the other hand, when the supply of a selection signal (selectionvoltage) to the scanning lines 302 is stopped under the above state, therelevant thin-film transistors 1 are turned off and the data lines 301and the pixel electrodes 303 coupled to the relevant thin-filmtransistors 1 become nonconductive to each other.

Therefore, with appropriate combinations of the supply and stop of aselection signal to the scanning lines 302 or the supply and stop ofdata to the data lines 301, desired images (information) can bedisplayed on the display surface (the side of the transparent substrate404) of the electrophoretic display device 200.

Especially, in the electrophoretic display device 200 according to thethird embodiment, by giving different colors to the electrophoreticparticles 421 and 422, images of multiple tones can be displayed.

Further, the electrophoretic display device 200 according to the thirdembodiment, which has the active-matrix device 300, can selectively turnon/off the thin-film transistor 1 coupled to a specific scanning line302. Therefore, crosstalk hardly occurs and, with the capability offaster circuit operation, high-quality images (information) can beobtained.

Furthermore, the electrophoretic display device 200 according to thethird embodiment operates at a low drive voltage and therefore canachieve power saving.

In addition, the electrophoretic display device 200 according to thethird embodiment, which is a so-called vertical-migration type usingmicrocapsules, is not limited to the vertical-migration type but can bea so-called horizontal-migration type wherein pixel electrodes 303 andthe common electrode 403 are provided laterally on the same substrate.Also, the electrophoretic display device 200 can be a device whereinelectrophoretic particles drift within spaces, each of which aresectioned with walls that are formed on a substrate, without usingmicrocapsules. Further, the application of a display device in which anactive-matrix device having the above-described thin-film transistor 1is not limited to the application to the above-described electrophoreticdisplay device 200 but includes the application to, for example, organicEL devices, liquid crystal display devices, etc.

Electronic Apparatus

The above-described electrophoretic display device 200 can be providedin various electronic apparatuses. Electronic apparatuses having theelectrophoretic display device 200 will be described below.

Electronic Paper

First, a fourth embodiment of the invention wherein the electronicapparatus according to the fourth aspect of the invention is applied toan electronic paper will be described.

FIG. 7 is a perspective view showing the fourth embodiment wherein theelectronic apparatus according to the fourth aspect of the invention isapplied to an electronic paper.

An electronic paper 600 shown in FIG. 7 has a main body 601 that isconfigured of a rewritable sheet having the same texture and flexibilityas paper and a display unit 602.

In the electronic paper 600, the display unit 602 is configured of theabove-described electrophoretic display device 200.

Display

Next, a fifth embodiment of the invention wherein the electronicapparatus according to the fourth aspect of the invention is applied toa display.

FIGS. 8A and 8B are diagrams showing a fifth embodiment wherein anelectronic apparatus according to the fourth aspect of the invention isapplied to a display. FIG. 8A is a cross section and FIG. 8B is a planview.

A display 800 shown in FIGS. 8A and 8B has a main body 801 and anelectronic paper 600 provided to be detachable from the main body 801.In addition, the electronic paper 600 has the above-describedconfiguration, that is, the same configuration as shown in FIG. 7.

The main body 801 has an insertion slot 805 on the side (right side inFIG. 8A), from which the electronic paper 600 can be inserted, and twopairs of feeding rollers 802 a and 802 b inside. When the electronicpaper 600 is inserted into the main body 801 through the insertion slot805, the electronic paper 600 is set in the main body 801, sandwichedbetween each pair of feeding rollers 802 a and 802 b.

Further, on the display surface (the near side in FIG. 8B) of the mainbody 801, a rectangular opening 803 is formed, wherein a transparentglass plate 804 is mounted. With such a configuration, the electronicpaper 600 set inside the main body 801 can be seen from outside. Thatis, the display surface of the display 800 is configured by showing theelectronic paper 600 that is set inside the main body 801 through thetransparent glass plate 804.

Further, on the edge on the insertion side (left side in FIG. 8A) of theelectronic paper 600, a terminal 806 is provided. Inside the main body801, a socket 807 to which the terminal 806 is coupled when theelectronic paper 600 is set in the main body 801 is provided. To thesocket 807, a controller 808 and an operation unit 809 are electricallycoupled.

In the above display 800, the electronic paper 600 is provided to bedetachable from the main body 801 and therefore can be used as aportable device when removed from the main body 801.

Further, in the above display 800, the electronic paper 600 isconfigured of the above-described electrophoretic display device 200.

In addition, the electronic apparatus according to the fifth embodimentof the invention is not limited to the above devices but includes:televisions, viewfinder or direct-view videotape recorders, carnavigation devices, pagers, electronic organizers, calculators,electronic newspapers, word processors, personal computers,workstations, videophones, POS terminals, touch-panel apparatuses, etc.As the display unit of the foregoing electronic apparatuses, theelectrophoretic display device 200 can be applied.

The method for manufacturing an organic semiconductor device, as well asthe organic semiconductor device, the electronic device, and theelectronic apparatus according to the embodiments of the invention,which have been described with reference to the drawings, are notlimited to the above examples.

1. An organic semiconductor device, comprising: a gate electrode; asource electrode; a drain electrode; an organic semiconductor layer; agate insulation layer that insulates the source electrode and the drainelectrode from the gate electrode; a substrate that supports the gateelectrode, the source electrode, the drain electrode, the organicsemiconductor layer, and the gate insulation layer; and an underlayerthat contains an organic polymer material having a liquid crystal core,the underlayer being oriented in a specific direction and formed betweenthe substrate and the organic semiconductor layer so as to orient theorganic semiconductor layer along the orientation of the underlayer. 2.The organic semiconductor device according to claim 1, wherein theorientation of the underlayer is approximately parallel to a directionfrom the source electrode to the drain electrode.
 3. The organicsemiconductor device according to claim 1, wherein the organicsemiconductor layer contains a polymer organic semiconductor material.4. The organic semiconductor device according to claim 1, wherein theorganic semiconductor layer is configured of an organic semiconductormaterial containing mainly an aryl group.
 5. An electronic devicecomprising the organic semiconductor device according to claim 1.